<?php

require_once 'HTMLPurifier/TagTransform.php';

/**
 * Transforms FONT tags to the proper form (SPAN with CSS styling)
 * 
 * This transformation takes the three proprietary attributes of FONT and
 * transforms them into their corresponding CSS attributes.  These are color,
 * face, and size.
 * 
 * @note Size is an interesting case because it doesn't map cleanly to CSS.
 *	   Thanks to
 *	   http://style.cleverchimp.com/font_size_intervals/altintervals.html
 *	   for reasonable mappings.
 */
class HTMLPurifier_TagTransform_Font extends HTMLPurifier_TagTransform
{
	
	var $transform_to = 'span';
	
	var $_size_lookup = array(
		'0' => 'xx-small',
		'1' => 'xx-small',
		'2' => 'small',
		'3' => 'medium',
		'4' => 'large',
		'5' => 'x-large',
		'6' => 'xx-large',
		'7' => '300%',
		'-1' => 'smaller',
		'-2' => '60%',
		'+1' => 'larger',
		'+2' => '150%',
		'+3' => '200%',
		'+4' => '300%'
	);
	
	function transform($tag, $config, &$context) {
		
		if ($tag->type == 'end') {
			$new_tag = $tag->copy();
			$new_tag->name = $this->transform_to;
			return $new_tag;
		}
		
		$attr = $tag->attr;
		$prepend_style = '';
		
		// handle color transform
		if (isset($attr['color'])) {
			$prepend_style .= 'color:' . $attr['color'] . ';';
			unset($attr['color']);
		}
		
		// handle face transform
		if (isset($attr['face'])) {
			$prepend_style .= 'font-family:' . $attr['face'] . ';';
			unset($attr['face']);
		}
		
		// handle size transform
		if (isset($attr['size'])) {
			// normalize large numbers
			if ($attr['size']{0} == '+' || $attr['size']{0} == '-') {
				$size = (int) $attr['size'];
				if ($size < -2) $attr['size'] = '-2';
				if ($size > 4)  $attr['size'] = '+4';
			} else {
				$size = (int) $attr['size'];
				if ($size > 7) $attr['size'] = '7';
			}
			if (isset($this->_size_lookup[$attr['size']])) {
				$prepend_style .= 'font-size:' .
				  $this->_size_lookup[$attr['size']] . ';';
			}
			unset($attr['size']);
		}
		
		if ($prepend_style) {
			$attr['style'] = isset($attr['style']) ?
				$prepend_style . $attr['style'] :
				$prepend_style;
		}
		
		$new_tag = $tag->copy();
		$new_tag->name = $this->transform_to;
		$new_tag->attr = $attr;
		
		return $new_tag;
		
	}
}

